Unify the plan to current priors; scrub the stale hold-out framing

The plan still read as though a Stage 19 burn were queued and Tier C were the
last gate before it. That framing predates the four audits.

Current prior stated up front: LegalBench-RAG is NOT the main bed - no case law,
no citations, no courts, so the citation web, court hierarchy and attested
characterization are structurally unmeasurable there, and F1 showed its
retrieval numbers are substantially a query-format artifact. It gets closed out,
not extended.

Phases replaced by an explicit priority order: harden the deterministic
structure layer, then premise #1's checker-family crossing (both in flight),
then free re-tests on banked data, then the case-law bed where the thesis
actually lives, then the arms never run, then the structure round's composed
ablations. LegalBench closeout drops to last and is explicitly "not a gate for
anything": Tier C answers whether G+ctx was ever separable from plain G, and the
hold-out burn is a separate decision rather than something queued behind it.
File the CRLF defect upstream regardless.

Principle 8 (nothing retired on a deterministic proxy) now carries the full
retirement standard. Structure-round doc re-pointed at priority 6.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01H9ToHYJVDxfeJcJwdzrP2H